Didn't realise they had a 'main fuse'?
When you say 'cleaning' have you had the lower case off?Maybe you've knocked one of the ribbon cable connectors off by accident?(happened to me)
Sounds like possible liquid ingress. Model number is of little use as Apple used numerous logic boards inside the same model numbers, I believe the A1286 for example could be any 1 of 6.
If this is a genuine query then you would need the number from the logic board as in 820-???? Not easy to find with the naked eye but is printed on the board itself. You could also try and find it here.
Enter your serial number and look for logic board in the list, if it's there google, the provided Apple part number and you should be able to find the required 820-???? number.